Aluminum-manganese alloys



United States Patent Office 3,341,368 Patented Sept. 12, 1967 3,341,368 ALUMINUM-MANGANESE ALLOYS Raymond Chevigny, 1 Ave. Alsace-Lorraine, Chambery, France, and Jean Louis Mercier, Fonchoma, Issoire,

rance No Drawing. Filed Feb. 13, 1964, Ser. No. 344,533 Claims priority, application France, Feb. 14, 1963, 924,834 4 Claims. (Cl. 1482) This invention relates to an improvement in aluminummanganese alloys and in the method of processing same. Alloys defined by the symbol A-Ml, in accordance with norms Afnor Nos. A-02.001 and A02.002, are well known. Their compositions, in percent by weight, may

be illustrated as follows:

Percent Manganese From 0.8 to 2. Iron Up to 0.4. Silicon Up to 3. Copper Up to 0.1.

It is also known to increase the iron content of such alloys up to about 1% in order to reduce the tendency for the grain to become enlarged.

These alloys find use, after being annealed and rolled or rolled with semi-hard hammer-hardening or forging, for the making of sheets of a metal in the form of boiler plate, or for stampings or cuttings.

However, dished or cupped members obtained by stamping or by a type of embossing, mandrel or roll forming (referred to in French more appropriately as repoussage) (hereinafter referred to as mandrel forming) of sheets of tempered A-Ml alloy are characterized by a fault which consists of the appearance of abnormal protuberances of material referred to in the trade as horns. The degree of horn formation is obtained as a percentage from the equation:

D percent- WHID in which H is the height of the tallest horn in the cup, h, is the height of the various openings between the horns, n is the number of horns and H is the average height of the cup. C percent is thus the percentage of the height of the cup affected by the defect.

In the stamping process, four large horns directed at 50 grades or 45 from the direction of rolling are observed. If the cast plates are heat treated over a long period of time at a high temperature, such as for 24 to 28 hours at a temperature of -600-620 C., the fault can be appreciably reduced.

In the mandrel forming process, only two horns are observed. These will be perpendicular to the rolling diidentical in character are employed the above equation.

The present invention is addressed to substantially reducing the formation of horns during the stamping or the mandrel forming (repoussage) of sheets of A-Ml alloy and it is an object of this invention to provide a method and means for accomplishing same.

It is also an object of this invention to produce sheets obtained by application of the foregoing process and to produce articles from said sheets by stamping and/or mandrel forming.

In accordance with the practice of this invention the improvements are achieved by at least one of the following steps with the steps given in the order of higher importance:

1) Making use of an alloy having a silicon content between 0.2% and 0.4%;

(2) subjecting the plates cast from the alloy containing 0.2% to 0.4% silicon to prolonged heat treatment at an elevated temperature such as for a period of 36 to 48 hours at 600620 C.;

(3) Roughly shaping the sheet while hot without intermediate steps of cooling to ambient temperature;

(4) Applying an intermediate tempering process to the sheets being rolled thereby to reduce the degree of cold hammer-hardening before the final tempering to encourage a reduction in the formation of horns.

The invention will be described with. reference to the following examples which are given by way of illustration, but not by way of limitation.

Heretofore the silicon in A-Ml alloy was considered as a harmful constituent such that it was proposed to limit the amount of silicon to a maximum of 0.3%.

It has been discovered by the applicants, much to their surprise, that when silicon is present in an amount Within the range of 0.2% to 0.4%, the silicon. constituents are beneficial in that the silicon brings about an important reduction in the horns when sheets rolled from the alloy are stamped or mandrel formed.

The effect of the silicon content can be illustrated by three series of tests in which each of the series is carried out with a commercial AM1 alloy having its silicon content adjusted to the indicated values. Heat treatments in each series. The results given are the ultimate values from the series of tests.

In the first series of tests, the metal employed is of the following composition:

then roughly shaped at 520 C. without intermediate cooling and it is then hammer-hardened cold by It then receives the rfinal tempering treatment in a stationary heat treating furnace.

In the second series of tests, the metal is of the following composition:

Percent Iron 0.57 Manganese 1.10 Copper 0.1-0 Titanium 0.04 Aluminum To 100 The cast plate is heat treated for 36 hours at 600 C. and is then roughly shaped at 500 C. without intermediate cooling. It is hammer-hardened cold by and it then receives the final tempering treatment in a moving furnace.

The third series of tests are carried out on a metal having the following composition:

Percent Iron 0.65 Manganese 1.30 Copper 0.12 Titanium 0.05 Aluminum To 100 The heat treatment applied to the cast plate is for 36 hours at 620 C. followed by rough shaping at 530 C. without intermediate cooling. The final cold hammerhardening of 300% is performed and then the final tempering process in a moving furnace terminates the operation.

The results of these tests are given in the table:

following treatment when at a thickness of 3 mm. The process is terminated by rapid tempering.

From the foregoing, it will be seen that the effect of the presence of silicon is appreciable when silicon is present in an amount of about 0.2% and that optimum values are achieved when the silicon is present in an amount within the range of 0.25% to 0.35%. The results indicate that while improvements continue to be achieved at higher concentrations of silicon, there is no compensating effect secured by exceeding a silicon content of 0.4%.

The effect of heat treatment on the cast plates can be illustrated by Table II, which refers to an =A-M1 alloy of the following composition:

Percent Iron 0.65 Manganese 1.25 Copper 0.15 Titanium 0.04 Silicon 0.06

As a result of the low silicon content, there is experienced a very marked anisotropic defect so that the effect of heat treating the plates can be clearly shown. The conditions of conversion are as follows: rough shaping at 520 C. with or without intermediate cooling; hammer-hardening by 100% and 150%, and tempering in a stationary furnace.

TABLE II Abnormal mandrel forming horns, percent 12 to 13 6 to 8 Heat treatment:

24 hours at 590 C. 24 hours at 640 C.

The foregoing illustrates the importance of carrying out the heat treatment, or the so-called homogenization treatment, on the cast plates while at a high temperature and therefore of lengthening the duration of the treatment.

The effect of intermediate tempering during rolling is illustrated by Table III in which the first column represents an alloy having the following composition:

Percent Iron 0.65 Silicon 0.33 Copper 0.1-2 Manganese 1.30 Titanium 0.05 Aluminum To 100 TABLE III.-ABNORMAL MANDREL FORMING HORNS Without inter- With intermediate mediate tempering, tempering,

percent percent TABLE IV.COMPOSITION OF ALLOYS NOS. 1 TO 4 IN TABLE V Content percent Alloy No.

Iron Silicon Copper Manganese Titanium Hammer-Hardening oi- Alloy No.

Percent Manganese 1.21 Silicon 0.38 Iron 0.60 Copper 0.09

The alloy is homogenized for 36 hours at 600 C., rough shaped while hot until it is reduced to 5.5 mm. thickness, and cold rolled to a 25/10 mm. reduction. It is then subjected to an intermediate tempering treatment after which it is rolled to 12/10 mm. before receiving the final tempering treatment.

The sheets obtained give rise to mandrel forming horns of the order of 3.5% whereas, without the improvements provided by the process of this invention, the horns are generally of 7%.

It will be understood that the invention will include any process, any rolled sheet metal and any stamped or mandrel formed article obtained by employment of at least one of the features heretofore described, and it will be further understood that changes may be made in the details of composition, arrangement and operation without departing from the spirit of the invention, especially as defined in the following claims.

We claim:

1. In the method of reducing horns during the processing of aluminum-manganese alloys by stamping and by mandrel forming comprising the steps of casting plates of the aluminum-manganese alloy, said alloy consisting essentially of from 0.8 to 2.0 percent by weight manganese, up to 0.4 percent by weight iron, up to 0.1 percent copper, and containing 0.2 to 0.4 percent by weight silicon with 3,219,492 11/1965 Anderson a-aIIZIIII 6 the balance aluminum, heating the cast plates for from 36 to 48 hours at a temperature of about 600 to 620 C., and shaping the plates into sheets after said heat treatment whereby the shaping operation takes place without any cooling to ambient temperature occurring between the heat treatment and the shaping operation.

2. A method in accordance with claim 1 wherein a cold hammer-hardening operation is conducted after formation of said sheets, and wherein the sheets are subjected to a tempering heat treatment as a final processing step.

3. The product produced by the method of claim 1.

4. The method as claimed in claim 2 which includes an intermediate tempering step between shaping and cold hammer-hardening.

References Cited UNITED STATES PATENTS 3,219,491 11/1965 Anderson et al FOREIGN PATENTS 8/1957 Great Britain. 

1. IN THE METHOD OF REDUCING HORNS DURING THE PROCESSING OF ALUMINUM-MANGANESE ALLOYS BY STAMPING AND BY MANDREL FORMING COMPRISING THE STEPS OF CASTING PLATES OF THE ALUMINUM-MANGANESE ALLOY, SAID ALLOY CONSISTING ESSENTIALLY OF FROM 0.8 TO 2.0 PERCENT BY WEIGHT MANGANESE, UP TO 0.4 PERCENT BY WEIGHT IRON, UP TO 0.1 PERCENT COPPER, AND CONTAINING 0.2 TO 0.4 PERCENT BY WEIGHT SILICON WITH THE BALANCE ALUMINUM, HEATING THE CAST PLATES FOR FROM 36 TO 48 HOURS AT A TEMPERATURE OF ABOUT 600 TO 620*C., AND SHAPING THE PLATES INTO SHEETS AFTER SAID HEAT TREATMENT WHEREBY THE SHAPING OPERATION TAKES PLACE WITHOUT ANY COOLING TO AMBIENT TEMPERATURE OCCURRING BETWEEN THE HEAT TREATMENT AND THE SHAPING OPERATION. 